<template>
  <div class="pagination">
    <!-- 上 -->
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">上一页</button>
    <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo', 1)" :class="{ active: pageNo == 1 }">1</button>
    <button v-if="startNumAndEndNum.start > 2">···</button>

    <!-- 中间部分 -->
    <button v-for="(page, index) in continues" :key="index" @click="$emit('getPageNo', page + startNumAndEndNum.start - 1)" :class="{ active: pageNo == page + startNumAndEndNum.start - 1 }">{{ page + startNumAndEndNum.start - 1 }}</button>

    <!-- 下 -->
    <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
    <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo', totalPage)" :class="{ active: pageNo == totalPage }">{{ totalPage }}</button>
    <button :disabled="pageNo == totalPage" @click="$emit('getPageNo', pageNo + 1)">下一页</button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  name: 'Pagination',
  props: {
    pageNo: {
      type: Number,
    },
    total: {
      type: Number,
    },
    pageSize: {
      type: Number,
    },
    continues: {
      type: Number,
    },
  },
  // 计算属性
  computed: {
    // 总共多少页
    // 向上取整
    totalPage() {
      return Math.ceil(this.total / this.pageSize)
    },
    // 计算出连续的页码的起始数字与结束数字
    startNumAndEndNum() {
      // 解构
      const { continues, pageNo, totalPage } = this
      // 先定义两个变量存储起始数字与结束数字
      let start = 0
      let end = 0
      // 总页码没有连续页码多
      if (continues > totalPage) {
        start = 1
        end = totalPage
        // 总页码比连续页码多
      } else {
        start = pageNo - parseInt(continues / 2)
        end = pageNo + parseInt(continues / 2)
        // start出现0或者负数
        if (start < 1) {
          start = 1
          end = continues
        }
        // end大于总页码数
        if (end > totalPage) {
          start = totalPage - continues + 1
          end = totalPage
        }
      }
      return { start, end }
    },
  },
}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active {
  color: skyblue;
}
</style>
